1. Field of the Invention
This invention relates to rotary electric machines, and more particularly to a rotary electric machine capable of operation with any one of two differnt rated voltages.
2. Description of the Prior Art
Electric motors which are capable of operation with any one of two different rates voltages by properly changing over the connection of the external connection terminals are now available in the market. As representative of such motors, those disclosed in U.S. Pat. No. 3,602,748 and Japanese utility Model Appication Laid-open No. 49-42401 are known. Both of the motors disclosed in the publications comprise two kinds of jumper conductor holders, one for a low voltage operation and the other for a high voltage operation. The jumper conductor holder for the low voltage operation is coupled to a connection terminal holder when the motor is to operate with the lower rated voltage. In this case, the armature winding of the motor is connected in the double star (2.lambda.) connection mode. When, on the other hand, the motor is to operate with the higher rated voltage, the jumper conductor holder for the high voltage operation is coupled to the connection terminal holder, whereby the armature winding of the motor is connected in the star connection (.lambda.) mode. Thus, coupling of the selected one of the jumper conductor holders to the connection terminal holder changes over the connection, so that the motor can operate with the selected one of the two rated voltages which have the relation of 1:2.
However, in each of the prior art disclosures, the lead-out wires used for connecting the motor to the power source have already been connected to the jumper conductor holder selected depending on the connection mode. Therefore, the procedure for change-over from one of the connection modes to the other has been troublesome and time-consuming in that not only the jumper conductor holder coupled already to the connection terminal holder must be replaced by the other jumper conductor holder, but also the lead wires must also be replaced.
While the situation will not be so serious when the lead wires can be replaced relatively easily, it is quite difficult to change the lead wires connected already to the jumper conductor holder when the motor is of the type which is designed to operate in a liquid or a gas whose electrical insulation resistance is not so high. Therefore, when the motor is to operate in such a liquid or a gas, it has been necessary to prepare two kinds of jumper conductor holders each having the lead wires connected thereto already. Since the length of the lead wires is generally as large as 300 m to 400 m in the case of a submersible motor, the preparation of such two kinds of jumper conductor holders each complete with the lead wires has been undesirable from the viewpoint of the cost which is considerably high.